I suggest that you run SFC scan on the computer to see if fixes the issue. SFC (System File Checker) checks for any corrupt system files and tries to repair them. To do so, follow these steps.
The sfc /scannow command scans all protected system files and replaces incorrect versions with correct Microsoft versions.
Error log is located at:
Add pku2u and livessp to the Security Packages REG_MULTI_SZ key under regkey HKLM\System\CurrentControlSet\Control\Lsa, and reboot.
Windows 8 sleeps after few minutes when awaken by external USB keyboard